Communication session preservation in geographically redundant cloud-based systems

ABSTRACT

Methods and apparatuses, including computer program products, are described for preservation of communication sessions in a geographically redundant cloud-based environment. The system comprises a plurality of end point devices and a plurality of cloud-based system instances, each comprising one or more server computing devices. A first cloud-based system instance assigned a first physical address is configured to establish a communication session using the first physical address between a first end point device and a second end point device, and mirror information associated with the communication session to a second cloud-based system instance assigned a second physical address. The second cloud-based system instance is configured to detect a failure of the first cloud-based system instance during the communication session, take control of the communication session using the mirrored information, and maintain the communication session between the first end point device and the second end point device using the second physical address.

TECHNICAL FIELD

This application relates generally to methods and apparatuses, including computer program products, for communication session preservation in geographically redundant cloud-based systems.

BACKGROUND

Voice client devices and video client devices (such as VoIP or SIP end user devices) and peers currently establish communication sessions over internet networks to computing systems responsible for the authorization and treatment of those sessions. However, the computing systems in the network are inherently subject to failure due to a variety of reasons—including hardware failure, software failure, and/or network failure.

Call preservation, sometimes referred to as system High Availability (HA), within a VoIP or SIP network is typically performed by two computing systems sharing a same physical address (e.g., IP address) in the network. One system can be designated as the primary system for establishing and handling communication sessions, and the other system can be designated as the backup or redundancy system. When the primary system fails, the backup system can assume the physical address of the primary system—e.g., through use of a floating or virtual IP address—so that the end point devices and peers can continue to communicate using the affected communication sessions without experiencing a change or disruption to the sessions (e.g., dropped call, forcing a client device to place a new call into the network).

Recently, VoIP and SIP communication systems and techniques have been deployed on cloud-based platforms (e.g., the AWS platform available from Amazon, Inc.) that comprise a series of geographically distinct system instances. Such cloud platforms generally do not allow a system instance to share the physical address of another system instance. As a result, traditional session preservation techniques, such as sharing a physical address, cannot be used in a cloud-based environment.

SUMMARY

What is needed is a system and method to enable the preservation of communication sessions in cloud-based environments when certain disruptions occur, while allowing the physical address(es) associated with the communication session to change.

The technology, in one aspect, features a system for preservation of communication sessions in a geographically redundant cloud-based environment. The system comprises a plurality of end point devices and a plurality of cloud-based system instances, each comprising one or more server computing devices. A first cloud-based system instance assigned a first set of one or more physical addresses is configured to establish a communication session using at least one address in the first set of physical addresses between a first end point device and a second end point device, and mirror information associated with the communication session to a second cloud-based system instance assigned one or more second physical addresses. The second cloud-based system instance is configured to detect a failure of the first cloud-based system instance during the communication session, take control of the communication session using the mirrored information, maintain the communication session between the first end point device and the second end point device using at least one address in the second set of physical addresses.

The above aspect can include one or more of the following features. In some embodiments, each of the plurality of cloud-based system instances are in a different geographical location. In some embodiments, the addresses in the first set of physical addresses are different from the addresses in the second set physical addresses. In some embodiments, the communication session is a Session Initiation Protocol (SIP) session. In some embodiments, the communication session is a Voice-over-IP (VoIP) session. In some embodiments, the first end point device is a SIP User Agent (UA) and the second end point device is a SIP UA. In some embodiments, the first end point device is a SIP Peer.

Other aspects and advantages of the technology will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating the principles of the technology by way of example only.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages of the technology described above, together with further advantages, may be better understood by referring to the following description taken in conjunction with the accompanying drawings. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the technology.

FIG. 1 is a block diagram of a first embodiment of a system for preservation of communication sessions in a geographically redundant cloud-based environment.

FIG. 2 is a call flow diagram of an exemplary communication session preservation flow in a SIP peering session for a cloud-based environment.

FIG. 3 is a call flow diagram of an exemplary communication session preservation flow in a SIP client session for a cloud-based environment.

FIG. 4 is a block diagram of a second embodiment of a system for preservation of communication sessions in a geographically redundant cloud-based environment.

FIG. 5 is a call flow diagram of an exemplary communication session preservation flow when a signaling instance fails in a cloud-based environment.

FIG. 6 is a call flow diagram of an exemplary communication session preservation flow when a media instance fails in a cloud-based environment.

FIG. 7 is a block diagram of a second embodiment of a system for preservation of communication sessions in a geographically redundant cloud-based environment.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of a first embodiment of a system 100 for preservation of communication sessions in a geographically redundant cloud-based environment. The system 100 includes a plurality of SIP UA/Peer devices 102 a, 102 b, a communications network 104, and a cloud environment having a plurality of system instances 106 a, 106 b. Each system instance 106 a, 106 b can comprise one or more cloud-based computing devices and related software for performing certain session or call-related functionality, such as authorizing and authenticating SIP UAs/Peers that attempt to connect, providing dynamic routing and other dial-plan features, providing call-based applications such as voicemail and services like transcoding and call events (e.g., forwarding, simultaneous ringing), and storing information such as user profiles, service levels, and the like.

It should be appreciated that system instance 106 a and system instance 106 b are geographically distinct nodes in the cloud environment that are assigned sets of different physical addresses 108 a, 108 b respectively. The system instances 106 a, 106 b communicate with each other (e.g., either directly and/or using network 104) for mirroring, redundancy, and failover purposes as will be described in detail below. In this embodiment, the system instances can comprise signaling instances (i.e., responsible for controlling and managing the call session establishment), media instances (i.e., responsible for controlling and managing the transfer of audio/video in the call session), and/or hybrid signaling/media instances—and the address(es) of the instance can comprise addresses for both signaling and media or addresses for signaling. It should further be appreciated that, in some embodiments, the mapping between the two sets of physical addresses (e.g., between address(es) 108 a of system instance 106 a and address(es) 108 b of system instance 106 b) can be one-to-one, one-to-many, or many-to-one.

In one example using the system 100 of FIG. 1, SIP UA/Peer device 102 a wants to establish a communication session (e.g., call) with SIP UA/Peer device 102 b. Device 102 a connects to the cloud environment using communications network 104 and is registered to system instance 106 a (using physical address(es) 108 a) for handling the communication session. System instance 106 a authenticates device 102 a and transmits a SIP INVITE message to device 102 b. Device 102 b sends a 200 OK message back to system instance 106 a, and system instance 106 a transmits the 200 OK message to the originating device 102 a. Device 102 a acknowledges the 200 OK message, and the two devices 102 a, 102 b establish a communication session and begin transmitting media and signaling communications between each other via the system instance 106 a. During the communication session, system instance 106 a is in regular contact with system instance 106 b for the purpose of transmitting certain session-related information to system instance 106 b (e.g., call state information) so that system instance 106 b can take control of the session in the event that system instance 106 a experiences a failure.

FIG. 2 is a call flow diagram 200 of an exemplary communication session preservation flow in a SIP peering session for a cloud-based environment, using the system 100 of FIG. 1. As shown in FIG. 2, SIP UA/Peer device 102 a has established a SIP peering session with system instance 106 a. Device 102 a transmits a SIP Options message 202 to system instance 106 a (e.g., as a keepalive message for the session) and system instance 106 a returns a SIP 200 OK message 204 in response. Device 102 a also transmits a SIP Options message 206 to system instance 106 b and, because system instance 106 b is not currently configured to control the session but instead is acting as a backup, system instance 106 b returns a SIP 480 Unavailable message 208.

Device 102 a then sends a SIP Invite request message 210 (with SDP) to system instance 106 a System instance 106 a returns a SIP 200 OK response message 212 (with SDP) to device 102 a, indicating that the request was successful. System instance 106 a also transmits a mirror record 214 (e.g., a copy of the packets comprising the communication to/from device 102 a) to system instance 106 b for redundancy and failover purposes. Exemplary information that can be included in a mirror record includes, but is not limited to, call state information for the particular call session such as caller number and IP address, callee number and IP address, call ID, SIP protocol tags, contact addresses, media addresses, and the like.

At some point during the communication session between device 102 a and system instance 106 a, the instance 106 a experiences a failure as shown in FIG. 2. Because system instance 106 b is in constant contact with system instance 106 a, instance 106 b automatically detects that instance 106 a has failed and assumes control of the existing communication session with device 102 a using the protocol-specific details of the session. System instance 106 b transmits a SIP Invite request message 216 (with SDP) to device 102 a and device 102 a returns a SIP 200 OK message 218 (with SDP) acknowledging the invite. Because system instance 106 b had been regularly receiving mirror records from system instance 106 a, instance 106 b can continue the communication session from where system instance 106 a left off and without interruption. Device 102 a transfers control of the session over to system instance 106 b including any media stream address changes that may be necessary. It should be appreciated that the communication session between device 102 a and system instance 106 b uses the physical address(es) 108 b of system instance 106 b, and does not adopt or otherwise use the physical address(es) 108 a of the failed system instance 106 a. When the session concludes, device 102 a transmits a SIP Bye message 220 to system instance 106 b and instance 106 b returns a SIP 200 OK message 222 (with SDP) acknowledging the request to end the session.

In one example of transfer of control, the system instances 106 a, 106 b send HA packets to each other at a predetermined interval, e.g., once a second. Those packets include information such as: operational state (i.e., active, standby), communication status to the remote instance, as well as default router connectivity. Based on the message contents, as well as the absence of receiving those messages, a system instance can make an autonomous decision as to which system needs to become active. Once that decision is made, the system instance can declare itself as active and can begin the act of pulling all of the remote sessions over to itself using the mechanisms described herein.

In addition, the backup system instance can take control of the calls using the mechanism defined by the SIP protocol. Specifically, a REINVITE that matches an existing dialog can change the Contact Address and Media Addresses used in the call. The Contact address change can instruct the far end device to use that address for all future SIP signaling messages. A media address change will cause the far end to start sending media to the new addresses.

FIG. 3 is a call flow diagram 300 of an exemplary communication session preservation flow in a SIP client session for a cloud-based environment, using the system 100 of FIG. 1. As shown in FIG. 3, SIP UA/Peer device 102 a registers with system instance 106 a by transmitting a SIP Register request message 302 to system instance 106 a, which returns a SIP 200 OK message 304 in response. Device 102 a transmits a SIP Invite request message 306 (with SDP) to system instance 106 a to initiate a communication session (e.g., with SIP UA/Peer device 102 b). Instance 106 a returns a SIP 200 OK message 308 (with SDP) to indicate that the request was successful. System instance 106 a also transmits a mirror record 310 (e.g., a copy of the packets comprising the communication to/from device 102 a) to system instance 106 b for redundancy and failover purposes.

At some point during the communication session between device 102 a and system instance 106 a, the instance 106 a experiences a failure as shown in FIG. 3. Because system instance 106 b is in constant contact with system instance 106 a, instance 106 b automatically detects that instance 106 a has failed and assumes control of the existing communication session. with device 102 a using the protocol-specific details of the session.

However, system instance 106 b may not be able to communicate immediately with device 102 a (e.g., because device 102 a is located behind a network firewall). In this case, device 102 a detects that system instance 106 a has failed by transmitting a plurality of SIP Register messages 312, 314 to system instance 106 a and not receiving any acknowledgements from instance 106 a.

In this example, device 102 a has been pre-configured to connect to system instance 106 b with physical address(es) 108 b in the event that system instance 106 a fails. Accordingly, device 102 a transmits a SIP register message 316 to system instance 106 b and instance 106 b sends back a SIP 200 OK message 318. Once device 102 a has successfully registered with system instance 106 b, instance 106 b takes control of the communication session and transmits a SIP Invite message 320 (with SDP) to device 102 a. Because system instance 106 b had been regularly receiving mirror records from system instance 106 a, instance 106 b can continue the communication session from where system instance 106 a left off and without interruption.

In response to SIP Invite message 320, device 102 a transmits a SIP 200 OK message 322 to system instance 106 b AND transfers control of the session over to system instance 106 b including any media stream address changes that may be necessary. It should be appreciated that the communication session between device 102 a and system instance 106 b uses the physical address(es) 108 b of system instance 106 b, and does not adopt or otherwise use the physical address(es) 108 a of the failed system instance 106 a. When the session concludes, device 102 a transmits a SIP Bye message 324 to system instance 106 b and instance 106 b returns a SIP 200 OK message 326 (with SDP) acknowledging the request to end the session.

FIG. 4 is a block diagram of a second embodiment of a system 400 for preservation of communication sessions in a geographically redundant cloud-based environment. The system 400 includes SIP UA/Peer devices 402 a, 402 b; communications network 404; a plurality of signaling instances 406 a, 406 b, each assigned a set of physical addresses 407 a, 407 b respectively; and a plurality of media instances 408 a, 408 b, each assigned a set of physical addresses 409 a, 409 b respectively. It should be appreciated that, in this embodiment, the signaling instances control and manage the signaling aspect (e.g., setup, tear down) of the call session between, e.g., device 402 a and 402 b, while the media instances control and manage the media (i.e., audio/video) aspect of the call session. Also, in this embodiment, the signaling instances are assigned different sets of physical addresses from both each other and from the media instances.

In some circumstances, during a communication session, a signaling instance can experience a failure while the corresponding media instance maintains the current session (or vice versa). FIG. 5 is a call flow diagram 500 of an exemplary communication session preservation flow when a signaling instance fails in a cloud-based environment, using the system 400 of FIG. 4. As shown in FIG. 5, SIP UA/Peer device 402 a transmits a SIP Invite message 502 (with SDP) to signaling instance 406 a for the purposes of establishing a communication session with device 402 b. The signaling instance 406 a transmits an add command 504 (with the SDP) to media instance 408 a so that the media instance can manage the exchange of audio/video packets between the devices 402 a, 402 b. In response to the invite message, the signaling instance 406 a returns a SIP 200 OK message 506 (with the SDP) back to device 402 a. The signaling instance 406 a also transmits a mirror record 508 to signaling instance 406 b for redundancy and failover purposes. Once the call is setup, SIP UA/Peer device 402 a establishes a Real-Time Protocol (RTP)/Secure Real-Time Protocol (SRTP) session with media instance 408 a.

During the session, signaling instance 406 a experiences a failure, as shown in FIG. 5. Because signaling instance 406 b is in constant contact with signaling instance 406 a, signaling instance 406 b automatically detects that signaling instance 406 a has failed and assumes control of the signaling aspect of the existing communication session with device 402 a using the specific signaling details of the session. In addition, because media instance 408 a has not failed, there is no change in the RTP/SRTP session information.

To maintain the communication session, signaling instance 406 b transmits a SIP Invite request message 510 (with the SDP) to device 402 a and device 402 a returns a SIP 200 OK message 512 (with SDP) acknowledging the invite. Because signaling instance 406 b had been regularly receiving mirror records from signaling instance 406 a, signaling instance 406 b can continue the communication session from where signaling instance 406 a left off and without interruption. Device 402 a transfers control of the signaling aspect of the session over to signaling instance 406 b and the session continues. It should be appreciated that the communication session between device 402 a and signaling instance 406 b uses the physical address(es) 407 b of signaling instance 406 b, and does not adopt or otherwise use the physical address(es) 407 a of the failed signaling instance 406 a. When the session concludes, device 402 a transmits a SIP Bye message 514 to signaling instance 406 b and instance 406 b returns a SIP 200 OK message 516 (with SDP) acknowledging the request to end the session. Signaling instance 406 b then transmits a delete command 518 (with the SDP) to media instance 408 a.

FIG. 6 is a call flow diagram 600 of an exemplary communication session preservation flow when a media instance fails in a cloud-based environment, using the system 400 of FIG. 4. As shown in FIG. 6, SIP UA/Peer device 402 a transmits a SIP Invite message 602 (with SDP) to signaling instance 406 a for the purposes of establishing a communication session with device 402 b. The signaling instance 406 a transmits an add command 604 (with the SDP) to media instance 408 a so that the media instance can manage the exchange of audio/video packets between the devices 402 a, 402 b. In response to the invite message, the signaling instance 406 a returns a SIP 200 OK message 606 (with the SDP) back to device 402 a. The signaling instance 406 a also transmits a mirror record 608 to media instance 408 b for redundancy and failover purposes. Once the call is setup, SIP UA/Peer device 402 a establishes a Real-Time Protocol (RTP)/Secure Real-Time Protocol (SRTP) session with media instance 408 a.

During the session, media instance 408 a experiences a failure, as shown in FIG. 6. Because media instance 408 b is in constant contact with signaling instance 406 a, media instance 408 b is able to determine that media instance 406 a has failed.

To maintain the communication session, signaling instance 406 a transmits a SIP Invite request message 610 (with SDP) to device 402 a and device 402 a returns a SIP 200 OK message 612 (with SDP) acknowledging the invite. Signaling instance 406 a then transmits an add command 614 (with SDP) to media instance 408 b. Because media instance 408 b had been regularly receiving mirror records from signaling instance 406 a, media instance 408 b can continue the communication session from where media instance 408 a left off and without interruption. Device 402 a resumes the RTP/SRTP session, this time with media instance 408 b, and the communication session continues. It should be appreciated that the communication session between device 402 a and media instance 408 b uses the physical address(es) 409 b of media instance 408 b, and does not adopt or otherwise use the physical address(es) 409 a of the failed media instance 408 a. When the communication session concludes, device 402 a transmits a SIP Bye message 616 to signaling instance 406 a and instance 406 a returns a SIP 200 OK message 618 (with SDP) acknowledging the request to end the session. Signaling instance 406 a then transmits a delete command 620 (with the SDP) to media instance 408 b.

The above-described techniques are further applicable in a network paradigm that incorporates firewalls and/or Network Address Translation (NAT) devices in the signaling path between SIP UAs and the system instances in the cloud environment. FIG. 7 is a block diagram of another embodiment of a system 700 for preservation of communication sessions in a geographically redundant cloud-based environment. The system 700 includes a plurality of SIP UA/Peer devices 702 a, 702 b, a firewall/NAT device 703 a, 703 b coupled to a corresponding SIP UA/Peer device, a communications network 704, and a cloud environment having a plurality of system instances 706 a, 706 b. As noted above with respect to FIG. 1, each system instance 706 a, 706 b can comprise one or more cloud-based computing devices and related software for performing certain session or call-related functionality, such as authorizing and authenticating SIP UAs/Peers that attempt to connect, providing dynamic routing and other dial-plan features, providing call-based applications such as voicemail and services like transcoding and call events (e.g., forwarding, simultaneous ringing), and storing information such as user profiles, service levels, and the like.

It should be appreciated that system instance 706 a and system instance 706 b are geographically distinct nodes in the cloud environment that are assigned sets of different physical addresses 708 a, 708 b respectively. The system instances 706 a, 706 b communicate with each other (e.g., either directly and/or using network 704) for mirroring, redundancy, and failover purposes as described in detail above. In this embodiment, the system instances can comprise signaling instances (i.e., responsible for controlling and managing the call session establishment), media instances (i.e., responsible for controlling and managing the transfer of audio/video in the call session), and/or hybrid signaling/media instances—and the address(es) of the instance can comprise addresses for both signaling and media or addresses for signaling. It should further be appreciated that, in some embodiments, the mapping between the two sets of physical addresses (e.g., between address(es) 708 a of system instance 706 a and address(es) 708 b of system instance 706 b) can be one-to-one, one-to-many, or many-to-one.

In one example using the system 700 of FIG. 7, SIP UA/Peer device 702 a wants to establish a communication session (e.g., call) with SIP UA/Peer device 702 b. Device 702 a connects to the cloud environment via Firewall/NAT 703 a using communications network 704 and is registered to system instance 706 a (using physical address(es) 708 a) for handling the communication session. As can be appreciated, the Firewall/NAT 703 a modifies the messages transmitted from the SIP UA/Peer device 702 a by remapping an address assigned to the SIP UA/Peer device 702 a in the packets to another address. System instance 706 a authenticates device 702 a and transmits a SIP INVITE message to device 702 b via Firewall/NAT 703 b, which performs a similar remapping of an address of SIP UA/Peer device 702 b. Device 702 b sends a 200 OK message back to system instance 706 a, and system instance 706 a transmits the 200 OK message to the originating device 702 a. Device 702 a acknowledges the 200 OK message, and the two devices 702 a, 702 b establish a communication session and begin transmitting media and signaling communications between each other via the system instance 706 a. During the communication session, system instance 706 a is in regular contact with system instance 706 b for the purpose of transmitting certain session-related information to system instance 706 b (e.g., call state information) so that system instance 706 b can take control of the session in the event that system instance 706 a experiences a failure.

The above-described techniques can be implemented in digital and/or analog electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. The implementation can be as a computer program product, i.e., a computer program tangibly embodied in a machine-readable storage device, for execution by, or to control the operation of, a data processing apparatus, e.g., a programmable processor, a computer, and/or multiple computers. A computer program can be written in any form of computer or programming language, including source code, compiled code, interpreted code and/or machine code, and the computer program can be deployed in any form, including as a stand-alone program or as a subroutine, element, or other unit suitable for use in a computing environment. A computer program can be deployed to be executed on one computer or on multiple computers at one or more sites.

Method steps can be performed by one or more special-purpose processors executing a computer program to perform functions by operating on input data and/or generating output data. Method steps can also be performed by, and an apparatus can be implemented as, special purpose logic circuitry, e.g., a FPGA (field programmable gate array), a FPAA (field-programmable analog array), a CPLD (complex programmable logic device), a PSoC (Programmable System-on-Chip), ASIP (application-specific instruction-set processor), or an ASIC (application-specific integrated circuit), or the like. Subroutines can refer to portions of the stored computer program and/or the processor, and/or the special circuitry that implement one or more functions.

Processors suitable for the execution of a computer program include, by way of example, special-purpose microprocessors, and any one or more processors of any kind of digital or analog computer. Generally, a processor receives instructions and data from a read-only memory or a random access memory or both. The essential elements of a computer are a processor for executing instructions and one or more memory devices for storing instructions and/or data. Memory devices, such as a cache, can be used to temporarily store data. Memory devices can also be used for long-term data storage. Generally, a computer also includes, or is operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto-optical disks, or optical disks. A computer can also be operatively coupled to a communications network in order to receive instructions and/or data from the network and/or to transfer instructions and/or data to the network. Computer-readable storage mediums suitable for embodying computer program instructions and data include all forms of volatile and non-volatile memory, including by way of example semiconductor memory devices, e.g., DRAM, SRAM, EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto-optical disks; and optical disks, e.g., CD, DVD, HD-DVD, and Blu-ray disks. The processor and the memory can be supplemented by and/or incorporated in special purpose logic circuitry.

To provide for interaction with a user, the above described techniques can be implemented on a computer in communication with a display device, e.g., a CRT (cathode ray tube), plasma, or LCD (liquid crystal display) monitor, for displaying information to the user and a keyboard and a pointing device, e.g., a mouse, a trackball, a touchpad, or a motion sensor, by which the user can provide input to the computer (e.g., interact with a user interface element). Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, and/or tactile input.

The above described techniques can be implemented in a distributed computing system that includes a back-end component. The back-end component can, for example, be a data server, a middleware component, and/or an application server. The above described techniques can be implemented in a distributed computing system that includes a front-end component. The front-end component can, for example, be a client computer having a graphical user interface, a Web browser through which a user can interact with an example implementation, and/or other graphical user interfaces for a transmitting device. The above described techniques can be implemented in a distributed computing system that includes any combination of such back-end, middleware, or front-end components.

The components of the computing system can be interconnected by transmission medium, which can include any form or medium of digital or analog data communication (e.g., a communication network). Transmission medium can include one or more packet-based networks and/or one or more circuit-based networks in any configuration. Packet-based networks can include, for example, the Internet, a carrier internet protocol (IP) network (e.g., local area network (LAN), wide area network (WAN), campus area network (CAN), metropolitan area network (MAN), home area network (HAN)), a private IP network, an IP private branch exchange (IPBX), a wireless network (e.g., radio access network (RAN), Bluetooth, Wi-Fi, WiMAX, general packet radio service (GPRS) network, HiperLAN), and/or other packet-based networks. Circuit-based networks can include, for example, the public switched telephone network (PSTN), a legacy private branch exchange (PBX), a wireless network (e.g., RAN, code-division multiple access (CDMA) network, time division multiple access (TDMA) network, global system for mobile communications (GSM) network), and/or other circuit-based networks.

Information transfer over transmission medium can be based on one or more communication protocols. Communication protocols can include, for example, Ethernet protocol, Internet Protocol (IP), Voice over IP (VOIP), a Peer-to-Peer (P2P) protocol, Hypertext Transfer Protocol (HTTP), Session Initiation Protocol (SIP), H.323, Media Gateway Control Protocol (MGCP), Signaling System #7 (SS7), a Global System for Mobile Communications (GSM) protocol, a Push-to-Talk (PTT) protocol, a PTT over Cellular (POC) protocol, Universal Mobile Telecommunications System (UMTS), 3GPP Long Term Evolution (LTE) and/or other communication protocols.

Devices of the computing system can include, for example, a computer, a computer with a browser device, a telephone, an IP phone, a mobile device (e.g., cellular phone, personal digital assistant (PDA) device, smart phone, tablet, laptop computer, electronic mail device), and/or other communication devices. The browser device includes, for example, a computer (e.g., desktop computer and/or laptop computer) with a World Wide Web browser (e.g., Chrome™ from Google, Inc., Microsoft® Internet Explorer® available from Microsoft Corporation, and/or Mozilla® Firefox available from Mozilla Corporation). Mobile computing device include, for example, a Blackberry® from Research in Motion, an iPhone® from Apple Corporation, and/or an Android™-based device. IP phones include, for example, a Cisco® Unified IP Phone 7985G and/or a Cisco® Unified Wireless Phone 7920 available from Cisco Systems, Inc.

Comprise, include, and/or plural forms of each are open ended and include the listed parts and can include additional parts that are not listed. And/or is open ended and includes one or more of the listed parts and combinations of the listed parts.

One skilled in the art will realize the technology may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the technology described herein. 

The invention claimed is:
 1. A system for preservation of communication sessions in a geographically redundant cloud-based environment, the system comprising: a plurality of end point devices; and a plurality of cloud-based system instances each comprising one or more server computing devices; wherein a first cloud-based system instance assigned a first physical address is configured to: establish a communication session using the first physical address between a first end point device and a second end point device, and mirror information associated with the communication session to a second cloud-based system instance assigned a second physical address, wherein the mirrored information comprises call state information for the communication session; wherein the second cloud-based system instance is configured to: detect a failure of the first cloud-based system instance during the communication session, including determining that the failure of the first cloud-based system instance has occurred based upon packet data received from the first cloud-based system instance; take control of the communication session using the mirrored information including transmitting a communication session invite message to the first end point device and the second end point device and receiving an acknowledgment to the communication session invite message from the first end point device and the second end point device; and maintain the communication session between the first end point device and the second end point device using the second physical address.
 2. The system of claim 1, wherein each of the plurality of cloud-based system instances are in a different geographical location.
 3. The system of claim 1, wherein the first physical address and the second physical address are different.
 4. The system of claim 1, wherein the communication session is a Session Initiation Protocol (SIP) session.
 5. The system of claim 1, wherein the communication session is a Voice-over-IP (VoIP) session.
 6. The system of claim 1, wherein the first end point device is a SIP User Agent (UA) and the second end point device is a SIP UA.
 7. The system of claim 1, wherein the first end point device is a SIP Peer. 